Wetting layer of copper on the tantalum (001) surface

The hetero-epitaxial interface formed by copper deposited onto the tantalum (001) surface is studied by surface X-ray diraction and ab initio calculations. The analysis of the crystal truncation rods reveals the presence of a wetting layer of copper made of two atomic planes pseudomorphic to the tantalum substrate, with the upper most atomic planes signicantly deformed. These ndings are in total agreement with the results of density functional theory calculations. The presence of the wetting layer conrms a Stranski-Krastanov growth mode and is thought to explain the extremely fast atomic diusion of copper during the dewetting process in the solid state at high temperature.